Objectives: (1) To ascertain the extent to which modulation and/or modification of plasma membranal structure and function correlates with fetal toxic and/or teratogenic responsiveness. (2) To characterize the properties and behavior of plasma membranal regulatory enzymes from fetal tissues and, where possible, to compare behavior of enzymes from fetal tissues with the corresponding ones from the adult. (3) To obtain further insight into the biochemical basis for the occurrence of abnormal ectodermal development (AED) about the brain and spinal cord.